1. Field of the Invention
The invention relates to methods for producing pearlescent button blanks.
2. Description of the Prior Art
A large part of the millions of buttons manufactured each year for clothing and the like are produced from liquid polymerizable resins that contain light reflecting materials (which are characteristically platelets, or lamellae) for imparting pearlescence and iridescence to the finished buttons.
The resins are generally cast into large sheets which are polymerized to a solid, non-tacky state. Button blanks of a desired shape and size are punched, or blanked, from the large sheets and are subsequently machined to produce the finished buttons.
To produce the pearlescence in the polymerized resin sheets the sheets are subjected to various operations prior to or during polymerization, or both, which tend to orient the light reflecting platelets parallel to the surface of the sheets. The various operations include: (1) the casting of the resins between sealed glass plates which are then rocked or vibrated in a direction that is parallel to the major dimension of the plates, (2) centrifugal casting of the sheets within large drums and (3) extrusion of the resin mixture through a constriction which produces a shearing action on the resin.
All of the various methods for producing pearlescent button blanks produce large amounts of waste ligament during the punching operation. Additionally, the edges of many of the button blanks are chipped and the blanks must be discarded. The total amount of waste material produced in these operations may be as much as 22% to 28% of the volume of the cast sheets.